An air battery that uses oxygen as the cathode active material has advantages such as high energy density, easiness of reducing size and weight, etc. Therefore, it attracts attention as a high-capacity battery which exceeds lithium secondary batteries that are widely used now. Among air batteries, the lithium-air battery has become an active area of research due to its high capacity.
The lithium-air battery is able to charge and discharge since an oxidation-reduction reaction of oxygen is carried out in the cathode (air electrode) and an oxidation-reduction reaction of lithium is carried out in the anode. In the lithium-air secondary battery, it is considered that the following charging/discharging reactions proceed.
[Upon Discharging]
Anode:
Li→Li++e−
Cathode:
2Li++O2+2e−→Li2O2 
4Li++O2+4e−→2Li2O
[Upon Charging]
Anode:
Li++e−→Li
Cathode:
Li2O2→2Li++O2+2e−
2Li2O→4Li++O2+4e−
The lithium-air battery comprises, for example, the following: a cathode containing a carbonaceous material and a binder; a cathode current collector that collects current from the cathode; an anode containing an anode active material (such as metal or alloy); an anode current collector that collects current from the anode; and an electrolyte disposed between the cathode and the anode. Sometimes, a catalyst is contained in the cathode.
For example, in Patent Literature 1, a lithium-air battery comprising carbon and a binder as constitutional components is disclosed.
In Patent Literature 2, a method for producing an oxygen reduction catalyst is disclosed, which is not limited to the use for metal-air batteries. In particular, a method for producing an oxygen reduction catalyst is disclosed in Patent Literature 2, the catalyst containing a transition metal oxide in which the crystal lattice is expanded by introducing oxygen defects into the surface and replacing part of oxygen atoms on the surface by at least one of carbon atoms and nitrogen atoms. In Patent Literature 3, a fuel cell catalyst for the air electrode of fuel cells is disclosed, which is not for metal-air batteries.